var arr=[10,20,3,4,66,22,8]
// console.log(arr.length);
// arr.push(15)
// arr.unshift(30)
// arr.slice(1,0,5)
// console.log(arr);
// arr.splice(3,1)
for (var i =0;i <arr.length;i++){
    console.log(arr[i]);
}
for(var i in arr){
    console.log(arr[i]);
}
for (var i of arr){
    console.log(i);
}